Beware of old

There are many unwritten rules in the emotional tangle of human relationships. That our friends' lovers are off limits is one of the cardinals, but what happens when a friend's partner becomes their ex? With many of us meeting, flirting and seducing within the framework of our extended social group, it's likely that a good proportion of us will "share" an ex with a friend at some point, and the repercussions may prove considerably more complicated than we'd imagined.

"It's this whole thing about intimacy and creating triangles," says Paula Hall, a counsellor for Relate. "We like one-on-one relationships. When you start getting triangles it feels strange and uncomfortable." You have shared a relationship that was, in your eyes, unique and, says Hall, "when somebody else effectively has that relationship as well, your unique relationship has gone."

A number of years ago, I had a fling with a friend's most recent ex. It wasn't a calculated decision (our "union" came about in the small hours of a party's messy aftermath). She was over him, she said. But not so over him, I quickly learned, that she wasn't hurt. In a matter of weeks, the relationship had run its course. It was considerably longer before our friendship came close to being back on an even keel.

"Good old human suspicion," as Hall calls it, could be responsible for this, as one friend considers the other's motives in the context of their relationship and its demise. Even without this doubt, the delineation of your friendship has changed; someone who had previously been considered an emotional support is now an emotional rival, and there may be a sense, no matter how irrational, that your friend is now succeeding where you failed.

"A lot of people have difficulty in letting go of relationships at a deeper level," says psychologist Leila Collins of Middlesex University. You might not want it, she says, but you don't want anyone else to have it either. More than this, she adds, "If a friend gets involved with a person who, at a deeper level, they still think belongs to them, they see that as betrayal."

And it's that, as I discovered, that most puts a friendship at risk: a line has been crossed, a trust betrayed, and any residual anger felt about the end of the relationship is all too easily focused on that betrayal. "People are always jealous about their intimate relationships," says Hall, "and when you're talking friendships and boyfriends, you've got two intimate relationships at the same time." And in doubling the emotion, you're likely to be doubling the trouble.

Collins and Hall agree that timing has much to do with the repercussions on a friendship. If the previous relationship broke down some time ago, says Collins, it is easier to deal with a friend stepping into what was once your territory than if the pain is still acute. But while a sufficient mourning period may be enough to soften the blow, a safer option is to wait until that friend has moved on to another relationship.

In truth, you won't know how your friend will react until after the fact. The safest course of action, really, is to stay away. But, if Cupid's bow is loaded and aimed towards temptation, take a final warning from one who knows and consider carefully whether the price of passing passion is equal to the value of a good friendship.